Soft-Tissue Preservation in Miocene Frogs From Libros, Spain: Insights Into the Genesis of Decay Microenvironments

McNamara, Maria E.; Orr, Patrick J.; Kearns, Stuart L.; Alcalá, Luís; Anadón, Pere; Mollá, Enrique Peñalver

doi:10.2110/palo.2008.p08-017r

Cited by 73 publications

(108 citation statements)

References 90 publications

(130 reference statements)

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“…Exquisitely preserved fossil microbial biofilms retaining bacterial forms are found in some soft animal tissue fossils of Mesozoic and Cenozoic ages (9,(23)(24)(25). The lower Cambrian embryo shown in Fig.…”

Section: Discussionmentioning

confidence: 98%

Embryo fossilization is a biological process mediated by microbial biofilms

Raff

Schollaert

Nelson

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

127

116

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Fossilized embryos with extraordinary cellular preservation appear in the Late Neoproterozoic and Cambrian, coincident with the appearance of animal body fossils. It has been hypothesized that microbial processes are responsible for preservation and mineralization of organic tissues. However, the actions of microbes in preservation of embryos have not been demonstrated experimentally. Here, we show that bacterial biofilms assemble rapidly in dead marine embryos and form remarkable pseudomorphs in which the bacterial biofilm replaces and exquisitely models details of cellular organization and structure. The experimental model was the decay of cleavage stage embryos similar in size and morphology to fossil embryos. The data show that embryo preservation takes place in 3 distinct steps: (i) blockage of autolysis by reducing or anaerobic conditions, (ii) rapid formation of microbial biofilms that consume the embryo but form a replica that retains cell organization and morphology, and (iii) bacterially catalyzed mineralization. Major bacterial taxa in embryo decay biofilms were identified by using 16S rDNA sequencing. Decay processes were similar in different taphonomic conditions, but the composition of bacterial populations depended on specific conditions. Experimental taphonomy generates preservation states similar to those in fossil embryos. The data show how fossilization of soft tissues in sediments can be mediated by bacterial replacement and mineralization, providing a foundation for experimentally creating biofilms from defined microbial species to model fossilization as a biological process.bacterial ͉ developmental evolution ͉ metazoan origins ͉ taphonomy ͉ Cambrian

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Section: Discussionmentioning

confidence: 98%

Embryo fossilization is a biological process mediated by microbial biofilms

Raff

Schollaert

Nelson

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

127

116

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“…The preservation of bone marrow and muscles in amphibians from Miocene sulfur-rich lake deposits in Spain has been attributed to this process. [74][75][76] Analyses of older fossils, complemented by maturation experiments, have shown that over time the composition of animal and plant cuticles, for example, is transformed by cross-linking reactions into more stable longer chain hydrocarbons (in situ polymerization), which incorporates lipids, [77] a process enhanced in the presence of sulfide. This diagenetic change is time dependent, but accelerated by the elevated temperatures experienced by rocks at depth, and although it modifies the original chemical composition and internal structure of tissues, their external morphology remains largely intact.…”

Section: The Molecular Composition Of Tissues and Their Decay Environmentioning

confidence: 99%

“…Features known to be preserved through phosphatization include microbes, [78] cells and embryos with possible nuclei, [79] guts, [80] epidermis, [75] and muscles. [46,78,81,82] Experiments have revealed the importance of microbial activity in releasing phosphate and generating the necessary geochemical gradients to induce phosphatization in a decaying carcass.…”

Section: Authigenic Mineralization Saves Tissues Apparently Doomed Tomentioning

confidence: 99%

Soft‐Bodied Fossils Are Not Simply Rotten Carcasses – Toward a Holistic Understanding of Exceptional Fossil Preservation

et al. 2017

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Exceptionally preserved fossils are the product of complex interplays of biological and geological processes including burial, autolysis and microbial decay, authigenic mineralization, diagenesis, metamorphism, and finally weathering and exhumation. Determining which tissues are preserved and how biases affect their preservation pathways is important for interpreting fossils in phylogenetic, ecological, and evolutionary frameworks. Although laboratory decay experiments reveal important aspects of fossilization, applying the results directly to the interpretation of exceptionally preserved fossils may overlook the impact of other key processes that remove or preserve morphological information. Investigations of fossils preserving nonbiomineralized tissues suggest that certain structures that are decay resistant (e.g., the notochord) are rarely preserved (even where carbonaceous components survive), and decay-prone structures (e.g., nervous systems) can fossilize, albeit rarely. As we review here, decay resistance is an imperfect indicator of fossilization potential, and a suite of biological and geological processes account for the features preserved in exceptional fossils.

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“…sulfate reduction), for example, contribute to development of microenvironments in which minerals form in place of decomposing tissues. These preservational microenvironments, which geochemically differ in various ways from their immediate surroundings, may form internally or externally of carcasses (McNamara et al, 2009). Regardless, microenvironment development depends upon reductant and oxidant (i.e.…”

Section: Taphonomic Processesmentioning

confidence: 99%

“…1) include silicification Rice et al, 2002;Strang et al, 2016;Xiao et al, 2010), phosphatization Dornbos, 2011;McNamara et al, 2009;Schiffbauer et al, 2014a), pyritization Guan et al, 2016;Schiffbauer et al, 2014b), aluminosilicification (Cai et al, 2012;Orr et al, 1998), and preservation of tissues with carbonate (i.e. calcite and siderite) minerals Cotroneo et al, 2016).…”

Section: Taphonomic Processesmentioning

confidence: 99%

Exceptionally Preserved Fossil Assemblages Through Geologic Time and Space

Muscente¹,

Laflamme²,

Schiffbauer³

et al. 2016

Geological Society of America Abstracts With Programs

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Geologic deposits containing fossils with remains of non-biomineralized tissues (i.e. Konservat-Lagerstätten) provide key insights into ancient organisms and ecosystems. Such deposits are not evenly distributed through geologic time or space, suggesting that global phenomena play a key role in exceptional fossil preservation. Nonetheless, establishing the influence of global phenomena requires documenting temporal and spatial trends in occurrences of exceptionally preserved fossil assemblages. To this end, we compiled and analyzed a dataset of 694 globally distributed exceptional fossil assemblages spanning the history of complex eukaryotic life (~610 to 3 Ma). Our analyses demonstrate that assemblages with similar ages and depositional settings commonly occur in clusters, each signifying an ancient geographic region (up to hundreds of kilometers in scale), which repeatedly developed conditions conducive to soft tissue preservation. Using a novel hierarchical clustering approach, we show that these clusters decrease in number and shift from open marine to transitional and nonmarine settings across the Cambrian-Ordovician interval. Conditions conducive to exceptional preservation declined worldwide during the early Paleozoic in response to transformations of near-surface environments that promoted degradation of tissues and curbed authigenic mineralization potential. We propose a holistic explanation relating these environmental transitions to ocean oxygenation and bioturbation, which affected virtually all taphonomic pathways, in addition to changes in seawater chemistry that disproportionately affected processes of soft tissue conservation. After these transitions, exceptional preservation rarely occurred in open marine settings, excepting times of widespread oceanic anoxia, when low oxygen levels set the stage. With these patterns, nonmarine cluster count is correlated with non-marine rock quantity, and generally decreases with age. This result suggests that geologic processes, which progressively destroy terrestrial rocks over time, limit sampling of non-marine deposits on a global scale. Future efforts should aim to assess the impacts of such phenomena on evolutionary and ecological patterns in the fossil record.

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Soft-Tissue Preservation in Miocene Frogs From Libros, Spain: Insights Into the Genesis of Decay Microenvironments

Cited by 73 publications

References 90 publications

Embryo fossilization is a biological process mediated by microbial biofilms

Embryo fossilization is a biological process mediated by microbial biofilms

Soft‐Bodied Fossils Are Not Simply Rotten Carcasses – Toward a Holistic Understanding of Exceptional Fossil Preservation

Exceptionally Preserved Fossil Assemblages Through Geologic Time and Space

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